Digital storage oscilloscopes (DSOs) are designed to receive, capture and accurately display and analyze incoming signals as waveforms. Although oscilloscopes are precisely designed and constructed, many of the components may be slightly mismatched in their operating characteristics (i.e. they are not identical). This is because manufacturing tolerances allow for variation between components even though they are produced to the same specifications. Further, the operating characteristics of these components may vary as a function of temperature, operating lifetime and scope settings. Hence, inconsistencies may occur between readings when a characteristic of a particular oscilloscope has changed.
In order to overcome these variations, certain oscilloscopes—such as LeCroy digital oscilloscopes—self-calibrate in real time by measuring curves to characterize the varying components. A calibration is performed whenever the oscilloscope senses a change in any variable—such as temperature, time or scope settings—that might affect the characteristics of any one or more internal components of the digital oscilloscope. However, calibration is a time-consuming process, which results in a noticeable delay in processing in order to perform the calibration process. This calibration process therefore delays the ability to acquire and process other incoming data.
Furthermore, calibration measurements require switching several relays in order to properly connect the apparatus to perform this calibration. As these relays have relatively short life spans, excessive calibration increases the failure rate of these digital oscilloscopes.
Thus a need exists to speed the calibration process in DSOs and to do so without decreasing the life of the scope.
Accordingly, the present invention is a method and apparatus which allows for proper calibration of a DSO when a characteristic has changed, without a noticeable delay in the operation of the scope.